1. Field of the Invention
The present invention relates to an image forming apparatus and a medium feeding device.
2. Description of the Related Art
An image forming apparatus, such as a printer, a copying machine, and a facsimile machine, comprises a feeder unit as a means for absorbing a medium. The medium, such as paper or OHP sheets, accommodated in a medium cassette, is separated and fed one by one by a hopping roller. The fed medium abuts against a resist roller and a pressure roller so that the skew thereof is corrected. The medium is fed by the resist roller to an image forming section with an image drum and a transfer section. Also, the medium is fed to an image processing section having a read-out portion for reading out an image.
In order to create an accurate image, the transfer section and the resist roller are maintained in parallel with each other to keep the position of the image to be formed by the image forming apparatus. It is so important to maintain the parallelism between the transfer section and the resist roller that the feeder unit is made integral with and fixed to a main body of the apparatus.
When the medium is jammed during transportation, it must be removed. Accordingly, a cover of the main body is provided such that it can be opened and closed freely. If a medium is jammed, the user opens the cover and removes the medium to clear the jam.
However, when the user takes out the medium toward the user, it gives a reverse revolution force to the resist and pressure rollers. The medium may be torn by the load when taken out.
One of the resist and pressure rollers is disposed on a side of the cover and the other is disposed on a side of the main body. In this case, however, the resist and pressure rollers are separate when the cover is opened. Although the medium is easily removed to the side of the user, the resist and pressure rollers are separated by the open/close operation of the cover so that the pressure between the resist and pressure rollers is changed over years. Consequently, the medium is not fed in a stable condition afterwards. Also, a belt unit is provided for feeding the medium to the image forming section. However, the belt unit cannot be taken out to this side (user's side) easily because one of the resist and pressure rollers is disposed on the side of the main body.
In addition, when the user takes out the medium to this side, it provides a sensor lever constituting a medium detection sensor with a force in a direction opposite to a feeding direction of the medium. Consequently, the sensor lever becomes so rickety that the detection accuracy of the medium detection sensor is reduced.